Does Missile Defense Make Sense?

"USS Fitzgerald launches a Standard Missile-3." Credit: US Navy, 2012

Ballistic missile defense systems promise to protect us from nuclear annihilation. What's not to love? Quite a lot, it turns out.

Anti-ballistic missile (ABM) systems are designed to destroy ballistic missiles before they strike their targets. Most such systems have been close to potential targets for obvious reasons: The United States, for example, wants to protect its own territory and that's where it can put ABM systems. Some planned systems will aim to eliminate missiles during their boost phase, when they are slower moving and thus easier to hit. Both systems are expensive (the latter especially so) and, sad as it is, neither will ever work. Here's why.

According to a recent article in The Economist, in a 2017 test, the US's premiere ABM system, the GMD (for Ground-based Mid-course Defense) sent "four interceptors against one warhead [and] is assumed to [have] a 97% chance of a hit." Sounds great, right? But as the article goes on to note, "if merely a dozen missiles were volleyed at America, [they would] soak up more than $3bn of interceptors [even though] a single warhead would still have a 30% chance of getting acquainted with an American city." That means even 3% is an uncomfortably high failure rate. It's so high, in fact, that we would still need to rely on deterrence—which we already do. Aside from spending extra money, then, the system would do next to nothing to improve security.

It gets worse: Missile defenses might undermine deterrence. "If they don't work, how can they undermine deterrence?" you might ask. Excellent question! The answer is that foreign leaders might think they work, especially as we'd likely try hard to convince them that that is the case. Imagine the system's effectiveness rises to a solid 99%. North Korea might decide launching a nuclear-tipped ICBM is low-risk enough to actually do it. Now imagine that missile gets through. A nuclear war would likely result. Beyond that marginal encouragement of nuclear weapons use, the effect would be negligible. A serious nuclear power like Russia or China would always know it could simply launch enough missiles to overwhelm the US ABM system—or focus on their tactical use in poorly defended areas. They would not be encouraged by the ABM system, but nor would it provide additional deterrence or anything more than an imagined safety net.

What about boost-phase systems? Satellite-mounted lasers patched into a network of sensors that could monitor an ICBM's entire trajectory are perhaps the most promising. Lasers could be cheaper to fire and could recharge limitlessly (though not instantaneously), able to stop larger barrages of missiles. But this simply pushes the problem one level higher: What protects that intricate mesh of satellites, which need to be fine-tuned and spread all over the globe to provide reliable coverage? China demonstrated in 2007 that it was capable of shooting down satellites with lasers. Such a system would always be vulnerable to attack.

The problem with missile defenses is irresolvable: They must work so perfectly that they become impractical. Making them work (99.99%) perfectly, even if it proves possible, would be prohibitively expensive—and that's before taking into account that they also require perfect defense of the missile defense system itself! That is a further impossibility—one that would also divert fantastic sums of money the country would be better off using elsewhere, including for other defensive means. As much as we might like the idea of a protective blanket against a nuclear holocaust, missile defense is nothing more than a fantasy at the strategic level.